The invention relates to a technology for supplying a power supply voltage to a microprocessor such as a CPU.
Microprocessors include various devices such as CPUs installed in personal computers, workstations, game consoles, and the like. These microprocessors are provided with predetermined power voltages that are stabilized by voltage regulator circuits (hereinafter, referred to as voltage regulator circuits or regulator circuits). The power voltage supplied to a microprocessor is dependent on factors such as the microprocessor semiconductor manufacturing process. Microprocessors made with recently developed low-voltage processes require power voltages of approximately 1.2 only.
A number of vendors are currently offering a variety of such microprocessors. The microprocessors offered by these vendors instruct regulator circuits as to the level of power voltage required, by use of respective proprietary systems. Accordingly, regulator circuits are designed to accept instructions on power voltages from microprocessors. FIG. 7 shows a block diagram illustrating the configuration of a conventional microprocessor and regulator circuit.
As shown in FIG. 7, a microprocessor 60 and a regulator circuit 62 are connected to each other, for example, by five bits of signal lines 64 in parallel. The microprocessor 60 transmits a VID (Voltage ID) signal through the signal lines 64, which indicates to the regulator circuit 62 the level of power voltage Vdd required. The regulator circuit 62 generates the power voltage Vdd indicated by the microprocessor 60, and supplies this voltage to the microprocessor 60 through a power supply line 66. If, for example, the microprocessor 60 is replaced by a user in the apparatus incorporating the microprocessor 60 and the regulator circuit 62 (hereinafter, also referred to simply as a set), given that the new microprocessor 60 indicates the level of power required, it should still be possible to supply the optimum power voltage Vdd to the new microprocessor 60.
However, using conventional techniques, the VIDs of microprocessors 60 cannot be changed once they are fixed at the time when the microprocessor is manufactured as a set. Consequently, the power voltage supplied to a certain microprocessor will remain unchanged regardless of factors after shipment such as the amount of time that the apparatus is used.
In consideration of such post-shipment variations, microprocessor manufacturing vendors allow for possible worst case situations when they determine the power voltages or VIDs. Variations considered include long term changes in the microprocessor function, operating frequency, voltage drop occurring in the incorporated sets, and temperatures during use. This results in the microprocessors being provided with power supply voltages higher than that required to operate the microprocessors. Therefore, to reduce the power consumption of the microprocessors, it is desirable to set optimum power voltages according to the conditions of use of the microprocessor(s).